MEDIUM: connection: make xprt->rcv_buf() use size_t for the count

Just like we have a size_t for xprt->snd_buf(), we adjust to use size_t
for rcv_buf()'s count argument and return value. It also removes the
ambiguity related to the possibility to see a negative value there.

include/types/connection.h

@@ -268,7 +268,7 @@ enum {
  * and the other ones are used to setup and release the transport layer.
  */
 struct xprt_ops {
-	int  (*rcv_buf)(struct connection *conn, struct buffer *buf, int count); /* recv callback */
+	size_t (*rcv_buf)(struct connection *conn, struct buffer *buf, size_t count); /* recv callback */
 	size_t (*snd_buf)(struct connection *conn, const struct buffer *buf, size_t count, int flags); /* send callback */
 	int  (*rcv_pipe)(struct connection *conn, struct pipe *pipe, unsigned int count); /* recv-to-pipe callback */
 	int  (*snd_pipe)(struct connection *conn, struct pipe *pipe); /* send-to-pipe callback */

src/raw_sock.c

@@ -250,10 +250,10 @@ int raw_sock_from_pipe(struct connection *conn, struct pipe *pipe)
  * errno is cleared before starting so that the caller knows that if it spots an
  * error without errno, it's pending and can be retrieved via getsockopt(SO_ERROR).
  */
-static int raw_sock_to_buf(struct connection *conn, struct buffer *buf, int count)
+static size_t raw_sock_to_buf(struct connection *conn, struct buffer *buf, size_t count)
 {
-	int ret, done = 0;
-	int try;
+	ssize_t ret;
+	size_t try, done = 0;
 
 	if (!conn_ctrl_ready(conn))
 		return 0;

src/ssl_sock.c

@@ -5337,10 +5337,10 @@ reneg_ok:
  * avoiding the call if inappropriate. The function does not call the
  * connection's polling update function, so the caller is responsible for this.
  */
-static int ssl_sock_to_buf(struct connection *conn, struct buffer *buf, int count)
+static size_t ssl_sock_to_buf(struct connection *conn, struct buffer *buf, size_t count)
 {
-	int ret, done = 0;
-	int try;
+	ssize_t ret;
+	size_t try, done = 0;
 
 	conn_refresh_polling_flags(conn);